Engine Compression

Check engine compression with engine at normal operating temperature at specified cranking speed with all spark plugs removed and throttle wide open. Release fuel pressure. To release fuel pressure, remove fuel pump fuse (located in fuse block) and start engine until it stalls. Crank engine 2-3 times to release residual pressure.

On Q45 with Direct Ignition System (DIS), remove ornament cover and disconnect harness connector between ignition coil and power transistor.

On all models, crank engine at least 6 revolutions to determine engine compression. Compression reading should be as specified. See ENGINE COMPRESSION table.